Disposable scalpels having retractable blades have been proposed and produced in many different forms. The various different forms can, for present purposes, be considered to fall into two different categories; a first being scalpels in which the thumb operable slider projects through a side wall of the scalpel handle, and a second in which the slider projects through a slot in one edge that can be considered to be the top edge of the scalpel handle.
The first type of scalpel that has the slider projecting through a side wall of the handle is considered to suffer from a number of disadvantages, not least of which is that one designed for use by a right-handed person cannot easily be used by a left-handed person and vice versa. U.S. Pat. No. 6,254,621 describes a scalpel that is typical of this type.
The second type of scalpel that has the slider projecting through the top edge of the scalpel handle generally has the disadvantage that the scalpel handle is made in two parts that are subsequently secured together with the blade carrier inside the handle and the associated slider projecting through a slot in the top edge of the composite handle. Typical of this type of construction are the scalpels described in U.S. Pat. Nos. 5,330,493; 5,556,409; and 5,571,127. The two-part construction of the handle is considered by applicant to be undesirable for a variety of reasons not least of which is the fact that the handle could possibly come apart.
There are a number of factors that are independent of the type of construction that are considered to be desirable and that are present to greater or lesser extents in existing scalpels, these being factors that contribute to the scalpel blade being held firmly in its operative position; being held positively in its retracted inoperative position; and also a facility aimed at preventing reuse of a scalpel in an effort to avoid so-called sharps injuries to personnel that may come into contact with used medical equipment.